Various bimetallic salts and derivatives thereof have been employed in the preparation of scavengers or complexing agents for various ligands such as olefins, aromatics, carbon monoxide and the like as disclosed in U.S. Pat. Nos. 3,592,865; 3,647,843; 3,651,159; 3,754,047 and 3,755,487. One of the more popular bimetallic salts is cuprous aluminum tetrahalide (CuAlCl.sub.4) generally prepared by reacting a cuprous halide with an aluminum trihalide in a suitable solvent. Such commercially available cuprous halides generally contain some quantities of cupric halide which is believed to promote the formation of aromatic tars when the resultant cuprous aluminum tetrahalide is employed as the complexing agent. The present invention is believed to prevent or lessen the tendency for such complexing agents to form tars during adsorption processes employing such complexing agents.